#170633  by TikiTourer
 Mon Feb 22, 2021 7:22 pm
Hi all, this is my first post but I'm hoping some of the knowledgable folk around here can help me out.

I'm considering buying a motorhome to essentially live in full-time with the aim of living off-grid as much as possible, although staying at a powered site once or twice a week would be fine. With that, I'd try to limit the amount of moving around I'd do and I'd like have the ability to stay at a site for at least four days before moving on.

Some of the motorhomes I'm looking at purchasing either have no solar or limited solar so I may have to purchase the components required to get off the grid. I'd like some help nailing down all the components that I'd need to purchase if I start from scratch.

In terms of my power usage I think I'd be an average power user. It would only be myself living in the van and I'd try to get away from using gas as much as possible as I think a gas reliant system is expensive to run and I'd rather harness the power of the sun. My main power draws are likely to be an approx 85l compressor fridge, a blender to make smoothies, charging my phone, charging my laptop and a wireless modem. I work remotely online so charging my laptop regularly or keeping it on charge is a priority. I'm not sure I'd need to use a microwave while off-grid, but at times I may like to use a toaster, although I could possibly find other ways to toast some bread.

Anyway here's what I think I might need and would welcome anyone to critique or add to my list if I've forgotten anything.

1) Solar panels - Approx 400W PERC panels.
Any of the offerings from Sunnytech seem pretty good value, but I could consider two like this https://www.sunnytech.co.nz/store/defau ... /25/66/0/0

2) Batteries - Approx 400/ah.
For example two of these 6v models from AA Solar could work
https://aasolar.co.nz/product/aa-champi ... batteries/

Or I might go the lithium route and just get one of these 200 a/h models
https://www.sunnytech.co.nz/store/defau ... 121/69/0/0

3) Pure Sine Wave Inverter - This 1200W model seems good value to me
https://www.sunnytech.co.nz/store/defau ... 131/74/0/0

As does this one if I needed something larger
https://waveinverter.co.nz/shop/power-i ... -inverter/

4) Solar Charge Controller - This 40A model I think would do the trick
https://aasolar.co.nz/product/tracer-bn ... by-epever/

5) Battery monitor - Maybe this would do the job?
https://www.sunnytech.co.nz/store/defau ... 148/69/0/0

This one here also seems very common but I'm not sure which model I'd require 100A, 200A or 400A?
https://aasolar.co.nz/product/lcd-batte ... -votronic/

6) Dual Sensing VSR - Unsure of recommended brands/models. Does it even matter? Or would I be better off with just a regular VSR and not a dual sensing model?

That's all I can think of right now. Would I need anything else to build a solar/battery system from scratch on a motorhome that either has a very limited solar power supply or none at all?

All advice, critiques and thoughts are welcomed.

 #170634  by Derb
 Tue Feb 23, 2021 6:57 am
1st up. What total wattage of solar do you propose? Your posting only advises the type/size of panel. 400 a/hr of battery storage is futile if your solar is not up to the charging of these batteries. An electric toaster hammers batteries as does a coffee maker. Don’t take vehicle charging as a major contributor to your charging system - you will find short hops are unable to do much good to replace low batteries. Given your proposed living arrangements, use every available cm of roof area for solar. This will allow induction cooker etc use. Lithium batteries, whilst not cheap, are very good at fast recovery allowing full use of short windows of solar availability. Huge knowledge pool on this forum from all sides of the technology spectrum. There is no one “correct answer”. It is all about use expectations. Good luck.
 #170637  by Skiwi
 Tue Feb 23, 2021 7:36 am
Hi TikiTourer,

Welcome to the forum :TU

If you look at my signature below you will get an idea of our set-up, it is adequate for us without being spectacular. We are predominantly Weekend Warriors and enjoy all the comforts off home with this set-up (toaster, induction top cooker, microwave etc)

All below is IMHO:

Depending on where you intend too park 400w solar might be on the light side during winter, particularly if you intend to be in the Deep South

400Ah of AGM will give you 200Ah usable capacity and again may be a bit light during winter when you harvest a lot less solar. Additionally high draw devices places a significant strain on the AGM chemistry thus reducing their lifespan (we are upgrading to Lithium for this very reason) I think if you can afford it - go Lithium.

We upgraded from a 1000w MSW to a 2000w PSW inverter so we could run the toaster and microwave (in hindsight I would of held off doing this until I installed the Lithium)

VSR and DC to DC chargers only come into their own if you do a lot of (over 2 hours at a time) regular driving, I estimate mine contributes less than 5% to my power needs. If you are going to be staying at camp-grounds weekly(ish) I'd put that money onto a good 240V charger and top up at the camp-grounds overnight)

Virtually any battery monitor that gives volts, draw and SOC will do to get you started, I've only upgraded ours to get bells and whistles (no extra or better functionality)

Last edited by Skiwi on Tue Feb 23, 2021 7:48 am, edited 1 time in total.
 #170638  by Growlerbearnz
 Tue Feb 23, 2021 7:37 am
Our caravan has pretty much this exact system: 400W solar, 200Ah lithium, 85l fridge, however we don't use 240V appliances (but we make up for it with laptops, phones, a projector, stereo, disco lights... )

My advice would be to fit as much solar on the roof as you can. 400W is plenty in summer, but during a few rainy days in winter (in Northland!) we were losing ground, with the battery not recharging fully every day. In that particular case we would have made it for 5 days before the battery dropped below 30% overnight, but it wasn't all *that* dark and rainy, and we were in Northland.

We have 400W because that's as much as we can fit on the roof. If we had a larger caravan I'd go for at least 800W just for peace of mind in winter, but there's no such thing as "too many" solar panels. They are the cheapest part of this whole system too.
 #170642  by mattn
 Tue Feb 23, 2021 9:51 am
Agree with everything the guys above have posted. as far as power use, my guess is you laptop will be your biggest AH user (unless you drink as much coffee as me, then you can forget about solar for coffee making :D ) . A coffee machine or toaster might use 100AMp for 6 minutes (10AH), a laptop could use 5amp for 12hours (60AH). Power budgeting needs to be very care with the 'slow burn' - a lot of time with a small power draw - fridges are the well known one.

For you proposed use, you need a big battery charger. It does not need to be particularly smart - you need AMPS, the bigger the better (your solar has enough smarts to do the job smart does, your mains chargers job is boosting the batteries to 'nearly charged' and let solar finish them off ) . You need to be able to change you 400AH batteries overnight - that means a 50AMP or bigger charger.
 #170684  by Neddy
 Tue Feb 23, 2021 3:28 pm
Whether buying new or used, you don't get the luxury of starting with a completely blank slate. What you do start with will have a very big effect on where you go from there. Drawing up your "ideal" setup might be fun, but rest assured that it won't be what you end up with.
I really have only two recommendations :-
(1) Place a LOT more emphasis on solar power. Two 200w PERC panels would be a start, but if you could fit four........
(2) Place a LOT less emphasis on batteries and battery capacity. It seems counter-intuitive, but the more solar power you have, the less battery storage capacity you need - and the better your setup will work in Winter, poor light conditions and Southern latitudes.
Do it right and you won't need to plug into mains power. Ever.

 #170688  by Nut17
 Tue Feb 23, 2021 4:54 pm
Definitely with Neddy on this one. Solar is relatively inexpensive and the most sensible plan is to accurately measure the available roof space and fit as much capacity as you can. I am a fan of these controllers https://fazcorp.co.nz/collections/mppt- ... -ml-series as they have a dedicated lithium setting, and have customised settings along with a built in screen. Starting from scratch, I would not go past LiFePO4 lithium. The price is now very realistic at around $1200.00 for a 200 AH. Having to add to a system can end up being an expensive exercise, so planning and getting it right first time is definitely the best option.
 #170733  by Paul-Carter
 Wed Feb 24, 2021 8:23 am
Its always about budget. Just make sure that you do your layout with expansion in mind as money allows. Definitely go lithium, I wish I had but money did not allow.
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